Identification of Biochemically Distinct Properties of the Small Ubiquitin-related Modifier (SUMO) Conjugation Pathway in Plasmodium falciparum

Small ubiquitin-related modifiers (SUMOs) are post-translationally conjugated to other proteins and are thereby essential regulators of a wide range of cellular processes. Sumoylation, and enzymes of the sumoylation pathway, are conserved in the malaria causing parasite, Plasmodium falciparum. However, the specific functions of sumoylation in P. falciparum, and the degree of functional conservation between enzymes of the human and P. falciparum sumoylation pathways, have not been characterized. Here, we demonstrate that sumoylation levels peak during midstages of the intra-erythrocyte developmental cycle, concomitant with hemoglobin consumption and elevated oxidative stress. In vitro studies revealed that P. falciparum E1- and E2-conjugating enzymes interact effectively to recognize and modify RanGAP1, a model mammalian SUMO substrate. However, in heterologous reactions, P. falciparum E1 and E2 enzymes failed to interact with cognate human E2 and E1 partners, respectively, to modify RanGAP1. Structural analysis, binding studies, and functional assays revealed divergent amino acid residues within the E1-E2 binding interface that define organism-specific enzyme interactions. Our studies identify sumoylation as a potentially important regulator of oxidative stress response during the P. falciparum intra-erythrocyte developmental cycle, and define E1 and E2 interactions as a promising target for development of parasite-specific inhibitors of sumoylation and parasite replication.     

Syntheses of lipophilic chalcones and their conformationally restricted analogues as antitubercular agents

Lipophilic chalcones and their conformationally restricted analogues were synthesized and evaluated for their antitubercular efficacy against Mycobacterium tuberculosis H37Rv strain. Compounds 16, 24, 25a and 25c were found to be active MIC at 60, 30, 3.5 and 7.5 μg-mL^?1. In vitro cytotoxicity of compounds 16, 24, 25a, 25c and 26 in non-cancerous human epithelial kidney cell line (HEK-293) showed that most active compound 25a was approximately 2.85 times selective towards tubercular versus healthy cells whereas compound 24 was found to be 16 times selective.     

A mutation in the Cdon gene potentiates congenital nevus development mediated by NRASQ61K

Congenital nevi develop before birth and sometimes cover large areas of the body. They are presumed to arise from the acquisition of a gene mutation in an embryonic melanocyte that becomes trapped in the dermis during development. Mice bearing the Cdk4^R24C::Tyr‐NRAS^Q61K transgenes develop congenital nevus‐like lesions by post‐natal day 10, from melanocytes escaping the confines of hair follicles. We interbred these mice with the collaborative cross (CC), a resource that enables identification of modifier genes for complex diseases (those where multiple genes are involved). We examined variation in nevus cell density in 66 CC strains and mapped a large‐effect quantitative trait locus (QTL) controlling nevus cell density to murine chromosome 9. The best candidate for a gene that exacerbates congenital nevus development in the context of an NRAS mutation is Cdon, a positive regulator of sonic hedgehog (Shh) that is expressed mainly in keratinocytes.     

Biotransformation of eugenol to vanillin by a novel strain Bacillus safensis SMS1003

Due to the extensive applications of vanillin as flavored compound and increasing consumers concern for its natural and environment friendly mode of production, present work was focused on the selection of bacterial isolate capable of producing vanillin using eugenol biotransformation. Bacterial strain SMS1003 is evidenced as the potential strain for vanillin production and identified as Bacillus safensis (GeneBank accession no. MG561863) using biochemical tests and molecular phylogenic analysis of its 16S rDNA gene sequence. Molar yield of vanillin reached up to 10.7% (0.055?g/L) at 96?h of biotransformation using growing culture of B. safensis SMS1003 in following culture conditions: eugenol concentration 500?mg/L; temperature 37?°C; initial pH 7.0; inoculum volume 4%; volume of culture media 10%; and shaking speed 180?rpm. Vanillin was detected as the single metabolite with a molar yield of 26% (0.12?g/L) at 96?h using resting cells of B. safensis SMS1003. Product confirmation was based on spectral scan using photodiode array detector, Fourier-transform infrared spectroscopy, high-performance liquid chromatography, and mass spectroscopy.     

Multivalent Role of Human TFIID in Recruiting Elongation Components at the Promoter-Proximal Region for Transcriptional Control

1. Download high-res image (202KB)
2. Download full-size image